I just cant get these buggers to come up.

OK, the past couple of weeks I have planted them in the ground twice
and once in a big pot which I covered with plastic in the day and watered
every day.
Only 3 or 4 came up and they were the ones in the pot.
In Chicago area.
What is the deal with these guys?
fresh seeds just ordered.
I have tried in previous years too.
I thought they were a good cover crop????

Ross